As described in U.S. Pat. No. 3,726,306, slide control valves of this type are generally quite large having internal diameters ranging in size from 6 inches to 8 feet. Due to the services in which they are used, it is often necessary to repair or replace their internal parts including the slide. Obviously, it is desirable that this be done without taking the valve body out of the flow line in which it is installed.
In use, the slide of a valve of this type normally occupies a throttling position and is opened or closed depending on the type of valve or service, during start up, and in the event of an emergency. Since flow through the valve is normally in a vertical direction, the slide must be supported in the valve body; and due to the size of the slide and the impingement of the flow on the slide which partially closes the valve orifice, this vertical positioning of the valve imposes considerable load on the structure in the valve body on which the slide is supported. Consequently, there is a need to guide the slide or gate as it is moved between its flow controlling positions.
As shown in the aforementioned patent, the side edges of the slide are guidable reciprocally within guides between a seat ring or orifice plate and the body of the valve. The slide, guides, and orifice plate can be preassembled to permit them to be moved as a unit through a side opening in the body of the valve and then secured thereto to dispose the orifice in alignment with the flowway in order to smooth out turbulent flow through the valve. As explained in this patent, this structure not only permits the installation and removal of the internal parts as unit, but also minimizes distortion, binding, and wear by maintaining tolerances between the internal parts and the valve body due to thermal and mechanical stress.
In valves of this type where the slide is normally in throttling position, it is not necessary to maintain a tight seal between the slide and the seat surrounding the orifice in the orifice plate. The slide may have a T-slot connection with the stem of an actuator mounted on a bonnet removably installed on the body over the side opening, whereby the slide is free to shift into tight, load bearing engagement with the downstream guide surfaces.
In valves of this type manufactured and sold by Tapco, a division of Triten Corporation of Houston, Tex., the outer metal body is lined with a refractory material. Alternatively, the valve body may be lined with insulating material and the latter lined with refractory material. This results in a so-called "cold shell" design wherein external body temperatures are minimized.
Although these valves have experienced considerable success, they nevertheless require the fabrication of a large number of internal parts and considerable time and effort involved in assembling and disassembling them. The time and the cost involved in fabricating valves such as the type shown in the above-identified patent is significant; these costs are multiplied in the case of valves having larger internal diameters in large part because of the difficulties in maintaining precise tolerances across large diameters. These costs are further increased by valves such as a diverter valve having, for instance, a 96 inch inlet diameter and two side-by-side outlets each having an internal diameter of 96 inches such that the guides must be at least 16 feet long plus the distance the outlets are spaced apart. The difficulties in handling the internal parts of such a valve are alone a significant disadvantage of this construction.
The present invention is directed to such a valve in which an improved orifice plate, removable guides, and slide valve are provided so that they can be readily and easily inserted by sliding in place, and removed, repaired, and replaced through the bonnet without disassembling or removing the valve from the flow line.
The following represent the patent state of the art in addition to U.S. Pat. No. 3,726,306 mentioned above.
U.S. Pat. No. 4,531,539 discloses a slide valve whereby wear prone parts are removable without taking the valve off line. The valve is refractory insulated (Column 4, line 23).
U.S. Pat. No. 4,512,363 discloses a slide valve with guides held in place by a clamping action and is refractory lined (Column 3, line 33).
U.S. Pat. No. 4,458,879 discloses a slide valve with refractory lining using no screws or fasteners. Guides are maintained out of the flow path and held in place by a clamping action.
U.S. Pat. No. 5,123,440 discloses a slide valve with a slide or gate covered by a layer of refractory but uses clamping bolts.
U.S. Pat. No. 4,645,179 discloses a gate valve with self-aligning sealing gaskets which may be readily replaced.
U.S. Pat. No. 4,541,453 discloses a slide valve with refractory insulating material whereby the slide is held in tension.
U.S. Pat. No. 4,378,817 discloses a slide valve closure member held in place by guides and packed with refractory material but makes adjustments with fasteners.
U.S. Pat. No. 4,275,763 discloses a double slide valve with a refractory lining.
U.S Pat. No. 4,253,487 discloses a slide valve with a refractory lining.
U.S. Pat. No. 3,976,094 discloses a slide valve with a refractory layer but uses bolts.
U.S. Pat. No. 3,701,359 discloses a slide valve with refractory lining.